1. Field of the Invention
The present invention relates to radio frequency antennas. More particularly, the present invention relates to a compact broadband high definition television antenna.
2. Description of the Related Art
Prior art television antennas fall into two broad categories, the indoor antenna and the outdoor antenna. The indoor antennas are sometimes referred to as set-top antenna, and the outdoor antenna are commonly mounted to a mast located above the rooftop of a home or other building. Since US television broadcasts have occurred on both the VHF band (54 MHz to 216 MHz) and the UHF band (470 MHz to 890 MHz), prior art antenna structures have been design to receive in both of these bands. In fact, most prior art antenna systems have included two antenna structures, one for each band. For example, a common prior art indoor antenna includes a 7.5″ loop antenna for the UHF band and a pair of telescopic dipole elements for the VHF band. Similarly, prior art outdoor antenna have included a large vagi or log-periodic array for the VHF band, and various smaller structures for the UHF band, such as a small array, loops, bowtie structures, and others.
Where there are two separate antenna operating at different frequency bands, there is a need to combine these signals, so as to avoid the need for running two separate feed lines to the television receiver. Such combination has been achieved using filters, baluns, duplexers, diplexers, and other combining circuit designs. A combining circuit will always introduce some attenuation to the received signals. This attenuation may be overcome, to some extent, using a radio frequency (RF) amplifier located adjacent to the antenna. Since there are typically two distinct frequency bands, two separate radio frequency amplifiers are required. As the system is made more complex, it becomes more expensive. As the antenna structure is made larger to enhance RF performance, it becomes more expensive, more difficult to install, and less attractive to consumers.
The original US television standard was promulgated as the NTSC standard (National Television System Committee) in 1941, and is well known to those skilled in the art. The United States has promulgated a new standard, called the ATSC (Advanced Television Systems Committee), which is a digital broadcast format, commonly referred to as HDTV (High Definition Television). The ATSC standard is fully implemented on Feb. 17, 2009. Additionally, over the decades, the frequency bands have becomes more narrowly defined. For example, the higher UHF channels from 69-83 were reallocated in the 1980s to land mobile radio, which narrowed the UHF TV band to 470 MHz to 800 MHz. On the Feb. 19, 2009 date, UHF channels 52-69 will also be reallocated, again narrowing the band to 470 MHz to 698 MHz. In a similar vein, the VHF band is also being more narrowly used. The VHF band actually consists of two separate frequency bands, VHF-Low channels 2-6 (54 MHz to 88 MHz) and VHF-H channels 7-13 (174 MHz to 216 MHz). As the nation transitions to the ATSC standard, there will be very few remaining VHF-L broadcast broadcast stations, which implies that coverage of the VHF-L band is not required in many markets. Thus, it can be appreciated that there is a need in the art form an improved TV antenna apparatus adapted to the new ATSC standard, the more narrowly defined frequency bands, and the market demands for low cost, compact size, high RF performance, and simplicity in installation.